Most parasol heaters available today comprise a generally cylindrical base which may be used as a housing for a bottle or cylinder of butane or propane gas, a shaft extending upwardly from the housing for supporting a gas burner element, and a heat reflective dish or parasol supported above the burner, designed to throw heat downwards in an area around the base. The gas burner element may alternatively be any radiant heat element, including an electric radiant element. The problem with this design is exemplified in the schematic of FIG. 1 where it is evident that such heaters having a fixed parasol dish reflect the heat directly downwards to provide a reflected heat footprint, shown as the stippled area, forming a relatively small, generally circular region around the base of the heater. In this way the region where most heat is produced is immediately over the base, so that persons sitting around the base, which often has a table built over it, are not in fact in the region of maximum heat. This design is really more efficient at heating the area of the top table surface than the area around the table, or directly under the table, in effect. This problem has been addressed in one example by providing auxiliary heating elements under the table area, or around the sides of the base, providing a leg/foot warmer for persons sitting at a table over the base.
By tilting the parasol at an angle to the burner, it is possible to reflect heat produced by the burner downwardly and to one side of the base. Therefore persons standing or seated to one side of the parasol heater would receive much more direct heat from the heater. The circular table over the base could more easily be replaced by different table configurations or seating arrangements in a restaurant or patio setting where the parasol heater is to be used.
DE-102004034148 (F. Polzer GmbH) describes a parasol heater with a tilting parasol dish, in which the dish is mounted on simple hinged mounting which is centrally disposed above the gas burner element. The parasol dish is only capable of tilting at an angle, about one axis. The disadvantage of this arrangement is that when tilted to an angle of about 30°, the underside of the parasol dish contacts the top of the gas burner which restricts any further tilting movement. This means that heat still cannot be reflected very far from the base and the region immediately surrounding the base. The hinge mounting could be spaced more above the top of the burner, to let the parasol dish clear the burner when tilted, but the problem with this is that it would have to be spaced by at distance corresponding to at least the radius of the dish, making such an arrangement impractical, because the underside of the parasol dish has to be kept as close as possible to the top of the gas burner to stop heat escaping upwards and to efficiently reflect it downwards. FIG. 2 shows how a prior art parasol heater with a simple hinging parasol dish such as that described in DE-102004034148, provides a reflected heat footprint forming an ellipse, that extends over the base of the heater, and to one side, but only in a limited fashion, when fully tilted
Irish Patent No. S84796 describes an improvement to this arrangement whereby the parasol dish is connected to the radiant heat element by a mounting comprising a linkage which is adapted to allow the parasol dish to move in an arc over a side edge of the radiant heat element, whereby in use heat may be reflected therefrom in a parabola. As is evident from an inspection of FIGS. 3 to 5 such a parasol heater has a reflected heat footprint, which in contrast to the prior art arrangements of FIGS. 1 and 2, extends completely to one side of the base of the heater, in a parabola.
FIGS. 4 and 5 of S84796 replicated herein show how such an arrangement comprises a parasol heater having a base portion 10, a shaft portion 20, and a gas burner element 30. The parasol dish 40 is arranged on a four point hinge mounting 50 located to one side of the top of the gas burner 30. The four point hinge mounting 50 comprises a lower hinge bar 51, spaced from a lower hinge bar 52, both hingedly affixed to the top of the gas burner 30. A pair of crank arms 53 is pivotable with the lower hinge bar 51, and supports an upper hinge bar 54. The hinge bar 54 is hingedly affixed to one side of a triangular mounting bracket 55 on the underside of the parasol dish, as seen in FIG. 4. A connecting rod 56 completes the four point linkage, being hingedly fixed at one end 56a to the lower hinge bar 52, and at its other end 56b to an apex of the triangular bracket 55. The end 56b may in an alternative embodiment be slidably mounted in a fixed track or channel.
A mechanism provided on the same side of the burner 30 as the hinge mounting 50 is provided to cause the lower hinge bar 52 to rotate, which in turn causes the whole four point linkage to move to tilt the parasol dish 40 with respect to the gas burner 30. The lower hinge bar 51 carries a toothed gear 57 arranged to mesh with a worm gear 58 at the top of an operating rod handle 59. The user can twist the bottom of the handle 59, even when the gas burner is lit, to rotate the worm gear which causes the four point linkage to move and tilt the parasol dish to the desired angle. The gears 57, 58 provide a ratchet mechanism which resists further tilting of the dish unless the twist handle 59 is operated.
It is evident that the arrangement of S84796 advantageously allows for the focusing of heat generated by the burner at specific locations relative to the burner. However the mechanism by which the parasol dish is moved suffers from a number of disadvantages. Firstly, while it suggests that the user can twist the handle to move the parasol dish to a desired position even when the burner is lit, it has been found that the actuation of the worm gear linkage to effect any appreciable movement of the parasol requires an extended period of time. At all times during this actuation the user is very close to the burner and this can result in the user being exposed to too much heat for too long a time, thereby becoming very uncomfortable.
It has also been found that the use of the ratchet mechanism suffers in that on heating, the toothed gear 57 and worm gear 58 expand thereby restricting their relative movement to one another. This loss of smooth interaction can only be solved by turning the heater off and allowing it to cool sufficiently. In this way the ability to move the parasol heater during operation of the burner is reduced.
It will be further appreciated that such parasol heaters are intended for use in an outdoor environment. In such environments they become exposed to ambient conditions and unless the gearing mechanisms are fabricated from expensive rust resistant materials they can corrode or otherwise degrade through the exposure to inclement weather.
The present invention seeks to overcome the disadvantages with the prior art and to provide a parasol heater with a tilting parasol dish which reflects heat downwardly and to one side in the most efficient manner.